chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/tab_helper.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_TAB_HELPER_H_
 #define CHROME_BROWSER_EXTENSIONS_TAB_HELPER_H_
 
 #include <memory>
 #include <set>
 #include <string>
@@ skipping 12 matching lines @@
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 #include "extensions/browser/extension_function_dispatcher.h"
 #include "extensions/browser/extension_registry_observer.h"
 #include "extensions/browser/script_execution_observer.h"
 #include "extensions/browser/script_executor.h"
 #include "extensions/common/extension_id.h"
 #include "extensions/common/stack_frame.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
-class FaviconDownloader;
-
 namespace content {
 struct LoadCommittedDetails;
 class RenderFrameHost;
 }
 
 namespace gfx {
 class Image;
 }
 
 namespace extensions {
@@ skipping 241 matching lines @@
 
   // Generic weak ptr factory for posting callbacks.
   base::WeakPtrFactory<TabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TabHelper);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_TAB_HELPER_H_